<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>div三角</title>
    <style>
      .top {
        width: 0px;
        height: 0px;
        border: 100px solid transparent;
        /* background-color: #00f; */
        /* border-top: 100px solid transparent;
        border-right: 100px solid transparent; */
        border-bottom: 100px solid #00f;
        /* border-left: 100px solid transparent; */
      }

      .right {
        width: 0px;
        height: 0px;
        border: 100px solid transparent;
        /* background: #00f; */
        /* border-top: 100px solid transparent;
        border-right: 100px solid transparent;
        border-bottom: 100px solid transparent; */
        border-left: 100px solid #00f;
      }

      .bottom {
        width: 0px;
        height: 0px;
        border: 100px solid transparent;
        /* background: #00f; */
        border-top: 100px solid #00f;
        /* border-right: 100px solid transparent;
        border-bottom: 100px solid transparent;
        border-left: 100px solid transparent; */
      }

      .left {
        width: 0px;
        height: 0px;
        border: 100px solid transparent;
        /* background: #00f; */
        /* border-top: 100px solid transparent; */
        border-right: 100px solid #00f;
        /* border-bottom: 100px solid transparent;
        border-left: 100px solid transparent; */
      }
    </style>
  </head>
  <body>
    <div class="top"></div>
    <div class="right"></div>
    <div class="bottom"></div>
    <div class="left"></div>
  </body>
</html>
